Gear system

ABSTRACT

A reduction gear system includes a pair of sets of meshing pinions and internal gears having a substantially larger diameter than the pinions, a shaft connecting the internal gear of the first set to the pinion of the second set, a second shaft supporting the pinion of the first set, a third shaft supporting the internal gear of the second set, the axes of said second and third shafts being in alignment and parallel to but spaced from the axis of the first shaft. Additional parts of sets may be connected to the first pair. When used between the motor and drill bit of an oil well drill the shafts, pinions and gears are supported in an inner housing within an outer housing with a fluid mud passageway therebetween. The inner housing includes a grease chamber and the pressure of the grease is kept greater than the mud pressure by means of a piston surrounding the shaft at the top of the housing. The top of the top piston and bottom of the lower piston are exposed to the fluid mud and springs provide additional force urging the pistons toward one another.

This is a continuation, of application Ser. No. 568,496, filed 4/16/75now abandoned.

This invention relates to a gear system for use between axially alignedinput and output shafts and more particularly to such a gear system foruse between the motor shaft and drill bit used in deep oil welldrilling. Normally, there is a direct connection between the motor shaftand drill bit so that they rotate at the same angular velocity. Suchapparatus is shown in my U.S. Pat. Nos. 2,852,230 dated Sept. 16, 1956;3,076,514 dated Feb. 5, 1963; and 3,594,106 dated July 20, 1971. Undercertain circumstances, it is desirable to rotate the drill bit at aslower speed than the motor. In most cases, there are severe limitationsas to the diameter of the apparatus which can be used. For example, onlya six inch diameter space may be available. Because of this spacelimitation and also because of the severe operating conditions such ascaused by high temperatures, high loads and the drilling mud, theordinary reduction gearing of which I have knowledge are not suitable.For example, planet gearing of the restricted size necessary wouldrequire small delicate pinions with weak teeth. It is also desirable tobe able to provide a range of speed reductions instead of being limitedto a single reduction. The gear system must be simple and rugged and beable to withstand substantial compressive loads. The drilling mud mustbe kept out of the gear system and adequate lubrication must beprovided. This also requires that the drilling mud by-pass the gearsystem.

It is therefore an object of my invention to provide a gear system whichis small in transverse cross section and which is rugged and strong.

Another object is to provide such a gear system which is particularlysuited for use between the motor and bit in deep well drilling.

Still another object is to provide such a gear system which is welllubricated and which prevents leakage of drilling mud into the systemwhile permitting by-pass of the drilling mud around the gear system.

A further object is to provide such a system which may be connected intandem to permit more than one range of reduction.

A still further object is to provide such a system which is simple inconstruction and is relatively cheap to manufacture and maintain.

These and other objects of the invention will become apparent afterreferring to the following detailed description and attached drawings inwhich:

FIGS. 1a, 1b, 1c and 1d when connected on lines X--X, Y--Y and Z--Z is alongitudinal sectional view of the apparatus of my invention; and

FIG. 2 is a sectional view taken on line II--II of FIG. 1a.

Referring more particularly to FIGS. 1a and 2 of the drawings referencenumeral 2 indicates the outer housing of a motor, preferably a deep oilwell motor such as shown in my copending applications Ser. No. 545,866filed Jan. 31, 1975, entitled "Fluid Driven Motor Having Improved BladeConstruction" and Ser. No. 556,079 filed March 6, 1975, entitled "Inletand Outlet Ports and Sealing Means For A Fluid Driven Motor". The motor(not shown in detail) has a shaft 4, the lower end of which is connectedby a coupling 6 to a pinion shaft 8 having a pinion 9 at its lower end.A spacer 10 is attached to the inside of housing 2 and has an inwardlyextending frusto-conical portion 12 and an inner ring portion 14providing a small circumferential opening 16 around shaft 8. A pluralityof spaced apart openings 18 in portion 12 permits flow of fluid drillingmud from passageway 20 to passageway 22. External threads 24 areprovided on inner ring portion 14 for receiving an eccentric bushing 26.Bore 28 of bushing 26 has a main portion 28a of a maximum diameter, anintermediate diameter portion 28b and a minimum diameter portion 28c,all coaxial with pinion shaft 8. The outside surface 30 of bushing 26 iscylindrical with its axis parallel to but spaced from its bore axis. Atube 32 of uniform wall thickness closely surrounds the outer surface30. The bushing 26 is held in fixed position by means of centering keys34 spaced at 90° stations and by contact of tube 32 with housing 2 atthe remaining 90° station as best shown in FIG. 2. The centering keysare of substantially less length than bushing 26 and there are aplurality of axially aligned spaced apart keys at each station. The tube32 extends substantially the full length of the assembly. Ananti-rotation lug 35 is welded to the inside of housing 2. It will beseen that passageway 22 is provided between housing 2 and tube 32.

A piston 36 surrounds shaft 8 and extends to bushing 26 adjacent ring14. Packing 38 and 40 is provided to prevent passage of drilling mudpast the piston. Spring 44 is provided to keep the packing 38 tight. Toinsure that the pressure of grease in grease chamber 42 is at least asgreat or greater than the pressure of the drilling mud, spring 46 isprovided to urge the piston 36 away from its upper or entry end.Preferably the pressure is increased by 4 or 5 pounds. The shaft 8 isrotatably mounted in bushing 26 by means of bearings 48, 50 and 52 whichare separated by spacers 54 and 56 and held in axial position betweenthe shoulder at the junction of portions 28b and 28c of the bushing boreand lock nut 58 and lock washer 60 on shaft 8. The spacer 54 is held inplace by means of screw 61. Grease is provided to grease chamber 42 andto the gearing system through passageway 62 in bushing 26. A plug 64 isthreaded into the outer end of passageway 62.

A second eccentric bushing 66 having the same outside diameter aseccentric bushing 26 is mounted in tube 32 in abutting relationship withbushing 26. The main bore 68 (FIG. 1b) of bushing 66 has its axis offsetwith but parallel to the axis of pinion 9. A spacer 70 is positioned inbore 68 between bearings 72. Bore 74 at the upper end of bushing 66 hasan enlarged diameter with a cut out portion therein to receive aninternal gear 78 which meshes with pinion 9. A second pinion 80 isconnected to gear 78 by shaft 82 integral therewith. A bronze thrustwasher 84 is mounted between the face of pinion 9 and bushing 66 and abronze washer 86 is positioned within bore 68 at the upper end thereof.

A third eccentric bushing 88 is mounted in tube 32 in abuttingrelationship with eccentric bushing 66. The axis of its bore 90 is inalignment with the axis of pinion 9 but otherwise the construction andbearing arrangement is similar to that of eccentric bushing 66 and willnot be described in detail. A second internal gear 92 is received in theupper end of bushing 88 and is connected to a third pinion 94 by meansof shaft 96 integral therewith.

A fourth eccentric bushing 98 (FIG. 1c) which is functionally the sameas the second eccentric bushing 66 is mounted in abutting relationshipwith eccentric bushing 88. A third internal gear 100 is received in theupper end of bushing 98 and is connected to a fourth pinion 102 by meansof shaft 104 integral therewith.

A fifth or output bushing 106 is mounted in the output end of tube 32 inabutting relationship with bushing 98. A fourth internal gear 108 ismounted in the upper end of bushing 106 and is connected to an outputshaft 110 having its axis in alignment with the axis of pinion 9. Theshaft 110 is mounted in bearings 112, 114 and 116 in a manner similar toshaft 8. A grease passageway 118 having a plug 120 (FIG. 1d) at itsouter or lower end is provided at the output end of bushing 106. Aspacer 122 similar to spacer 10 is attached to the inside of housing 2and is threaded to bushing 106 at 124 with a small circumferentialopening 126 being provided between spacer 122 and shaft 110 foradmission of drilling mud. A packing gland 128 surrounds shaft 110 andextends to bushing 106 at the output end thereof. A spring 130 bearsagainst packing 131 to keep it tight.

The number of reduction stages may be greater or less than that shown.In all cases, however, at least a pair of sets of meshing pinions andinternal gears will be used with a shaft connecting the internal gear ofthe first set to the pinion of the second set, a second shaft supportingthe pinion of the first set and a third shaft supporting the internalgear of the second set.

The output shaft 110 may be connected to a drill bit 132 (not shown indetail) in case of deep well drilling or to other devices in other uses.

To assemble, each eccentric bushing first is assembled with all itsparts in place including the bearings and shafts. It will be seen (FIG.2) that each eccentric bushing has a pair of keyways 34a therein whichextend the full length thereof. The eccentric bushings are then slid oneby one over the keys 34 welded into tube 32. It will be seen that theassembled eccentric bearings form an inner housing.

The entire system within the tube 32 is grease tight with openings tothe various bearings and moving parts. The plug 64 is removed and greasepumped into the system. Plug 120 will be removed to permit escape of theair from the system. The plugs are then replaced with the grease beingunder pressure. In operation in a well the drilling mud will act againstthe piston 36 to drive it downwardly. Additional pressure is applied tothe piston 36 and grease by spring 46 to insure that the grease pressureis greater than the mud pressure so that any leakage will be grease fromthe system rather than mud into the system. While there has been shownand described one embodiment, it is to be understood that variousadaptations and modifications may be made within the scope of theinvention.

I claim:
 1. A reduction gear system comprising a pair of sets of meshingpinions and internal gears, said pair of sets including a first set anda second set, each of said sets including a single pinion in direct meshwith a single internal gear having a substantially larger diameter thansaid single pinion, the axis of said single pinion being parallel to theaxis of said single internal gear but spaced therefrom, a first shaftconnecting the internal gear of the first set to the pinion of thesecond set, a second shaft supporting the pinion of the first set, athird shaft supporting the internal gear of the second set, the axes ofsaid second and third shafts being in alignment and parallel to butspaced from the axis of the first shaft, and means for rotatablysupporting said shafts.
 2. A reduction gear system according to claim 1including at least one additional pair of sets of meshing pinions andinternal gears, the pinion of the first set of each pair being mountedon the shaft supporting the internal gear of the second set of the nextpreceeding pair.